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Viscera:Bladder and urethra (male and female)
The urinary bladder is a distal part of the urinary tract and is an extra-peritoneal structure located in the true pelvis. It is a reservoir for urine. It is lined with a rough, trabeculated transitional cell epithelium except at the trigone. Divisions * Apex: attached by the urachus * Base: lies below the Douglas pouch, covered only by peritoneum in the upper part, and the ureter enter at the upper outer corner. In female, the base is connected to the anterior vaginal wall, upper part of the cervix. * Inferolateral surface: slopes downwards and medially, meeting in midline and passes forward to the apex. Prior to the apex, space behind the pubic bone is called retropubic space of retzius, and contain loose fatty tissue and pubovesical ligaments that extend from the bladder neck to the pubic bone. * Neck: the lowest part of the bladder, where the base and inferolateral surface meet. The urethra pierces here at the internal urethral orifice surrounded by the internal urethral sphincter. In male, the prostate lies against this area. * Superior surface: covered by peritoneum which is displaced upwards with bladder distension. In male, the peritoneum passes back as the floor of the Douglas pouch, in female, it continues and reflects upward to the undersurface of the uterus. The trigone is a triangular area of smooth mucosa found on the internal surface of the base between the two urethral orifice and the internal urethra orifice. It is fixed on top of the prostate (in middle, age prostate can project into the bladder as the uvula) by the urethra, and least mobile. In female, it is stabilized by connective tissue at the front of the vagina. The ureters pierce the mucosal wall obliquely. Surrounding spaces: * perivescial space * prevesical between bladder and symphysis pubis (communicate with retroperitoneal compartment and presacral space) Relations - male * anteriorly - pubic symphysis * posteriorly - rectovesical pouch and rectum * inferiorly - prostate, obturator internus muscle, levator ani muscle * superiorly - peritoneum * laterally - ischioanal fossa Relations - female * anteriorly - pubic symphysis * posteriorly - vesicouterine pouch, uterus, cervix, vagina * inferiorly - pelvic fascia, perineal membrane * superiorly - uterus, peritoneum * laterally - ischioanal fossa Blood supply * arterial supply - superior and inferior vesical arteries (from anterior division o finternal iliac artery) * venous drainage - vesical venous plexus in the groove between bladder and prostate and then via, to the internal iliac veins Nerve supply * parasympathetic fibres via the pelvic splanchinic nerves * Sympathetic come from L1/2 of the cord via superior and inferior hypogastric plexuses (vasomotor and inhibitory to detrusor but stimulate sphincter) * Pain is via both parasympathetic and sympathetic paths way to the lateral spinothalamic tract. Lymphatic supply * accompanies blood vessels to the external iliac nodes, internal iliac nodes. Variant anatomy * double bladder - receives ipsilateral ureter and has separate urethra * septation - septum may divide the bladder internally into two or more compartments * agenesis - persistence of the cloaca * ureterocoele - dilation of the intravesical part of the ureter Female urethra is 4cm long, passing from neck of bladder to the external urethral meatus, embedded within the anterior wall of the vagina. Fibres of the pubovaginalis of the levator ani lie adjacent to the urethra, as it leaves the bladder. Blood supply: * upper part: superior and vaginal arteries * lower part: internal pudendal artery * veins drain to vesical plexus, prostate venous plexuses (in men) and uterovaginal plexuses (in woman). These then drain into pudendal vein. Lymph drainage: * pass to internal iliac node and some pass to external iliac group. Nerve supply: * inferior hypogastric plexuses and from the perineal branch of the pudendal nerve. * pelvic splanchnic for parasympathetic '''Male urethra '''is 20cm made up by prostatic, membranous and spongy parts which drain urine from the bladder. It commences at the internal urethral orifice in the trigone of the bladder and opens in the navicular fossa of the glans penis at the external urethral meatus, which is the narrowest part of the urethra. The male urethra can be divided four segments . * penile (spongy) urethra (16cm long): encased by corpus spongiosum of the penis. Just proximal to the external urethral meatus, the tip of the glans dilate called navicular fossa. It urethra is narrowest at the external meatus. * bulbar (bulbous) urethra: just after piercing of the perineal membrane, urethra traverses the root of the penis at right angles. * membranous urethra (1cm long): passes through the urogenital diaphragm (consists of sphincter urethrae and deep transverse perineal muscle). Contains cowpers glands. * prostatic urethra (3cm long): surrounded by the prostate gland; on its posterior wall lies the smooth muscle verumontanum Nerve supply * perineal nerve * inferior hypogastric plexuses Variant: * Duplication * Diverticulum * Posterior valve * Agenesis